## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

The required current is $2.8~A$
We can write an expression for the initial stored energy: $U_1 = \frac{1}{2}LI_1^2$ We can find the current when the stored energy is double: $U_2 = 2\times U_1$ $\frac{1}{2}LI_2^2 = 2\times \frac{1}{2}LI_1^2$ $I_2^2 = 2 I_1^2$ $I_2 = \sqrt{2}~ I_1$ $I_2 = (\sqrt{2})~ (2.0~A)$ $I_2 = 2.8~A$ The required current is $2.8~A$